1. Field of the Invention
The present invention relates to novel vanadium catalysts particularly well suited for the desulfurization of gases containing sulfur compounds and to a process for the preparation thereof. This invention also relates to a process for the treatment of gases, notably industrial gaseous effluents, containing objectionable sulfur compounds, to eliminate such sulfur compounds therefrom, especially via the Claus reaction, wherein the sulfur values are recovered in the presence of such catalysts and, in particular, of oxygen.
2. Description of the Prior Art
In the conventional Claus process, to which the present invention is not limited, sulfur is recovered from gases containing hydrogen sulfide in two stages. In a first stage, the hydrogen sulfide is burned in the presence of a regulated amount of air to convert a portion of the gas into sulfur dioxide. Then, in a second stage, the gaseous mixture obtained is conveyed into reactors in series containing a catalyst, over which the Claus reaction is carried out: EQU 2H.sub.2 S+SO.sub.2 .fwdarw.3/nS.sub.n +2H.sub.2 O
Numerous catalysts have been employed for this reaction. Thus, it has long been known to use an alumina-based catalyst therefor, such as described in French Patent No. 1,570,161. A mixture of titanium dioxide and alumina has also been described for such purpose (U.S. Pat. No. 4,141,962).
For reactions of this type, it too is known to this art to use catalysts which, other than alumina, contain vanadium oxide.
One of the disadvantages of the above catalysts is their instability relative to oxygen. Thus, when the gaseous effluent to be treated contains minor amounts of oxygen, such catalysts may be relatively rapidly deactivated, e.g., as a result of the sulfatation of their face surfaces. Their catalytic activity can then be irreversibly diminished.
A catalyst containing titanium dioxide deposited onto silica, or a catalyst based on titanium dioxide incorporating, as additives therefor, alkaline earth metal sulfates (U.S. Pat. No. 4,485,189), can also be used for such purpose. However, these catalysts also exhibit a lower activity during the treatment of oxygen-containing gases. Thus, it is important that the catalyst retain a satisfactory degree of activity in the presence of oxygen, because the industrial gases to be treated often contain small quantities thereof.